Telephone transmission system



P. M. GARDANIER.

TELEPHONE TRANSMISSION SYSTEM.

APPLICATION FILED JULY 23,1918.

1,3 55,957. Patnted Oct. 19, 1920.

5 SHEETSSHEET 1.

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Percy/7. Ga/dan/en y W Alf/y P. M. GARDANIER.

TELEPHONE TRANSMISSION SYSTEM.

APPLICATION FILED 'IULY 23,1918.

Patented Oct. 19, 1920.

5 SHEETSSHEET L kwwifsQw //7 vemon' Percy M Haida/flew. by

P. M. GARDANIER.

TELEPHONE TRANSMISSION SYSTEM.

Patented Oct. 19, 1920.

5 SHEETS -SHEET 3.

I APPLICATION FILED JULY 23.1918- 1,355,957.

//1 van/0K Percy M. Gardam'en fly P. M. GARDANIER.

TELEPHONE TRANSMISSION SYSTEM.

APPLICATION FILED JULY 23,1918- 1,355,957, Patented 0ct.19,1920.

5 SHEETS-SHEET 4- I 3 I I I NN a! E \E P. M. GARDANIER.

TELEPHONE TRANSMISSION SYSTEM.

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UNITED STATES PATENT OFFICE.

,PERCY M. GARD'ANIER, OF BAYSIDE, NEW YORK, ASSIGNOR TO WESTERN ELECTRIC COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATION OF NEW YORK.

TELEPHONE TRANSMISSION SYSTEM.

Specification of Letters Patent.

Patented Oct. 19, 1920.

Application filed July 23, 1918. Serial No. 246,317.

To all whom it may concern:

Be it known that I, PERCY M. GARDANIER, a citizen of the United States, residing at Ba-yside, in the county of Queens, State of New York, have invented certain new and useful Improvements in Telephone Transmission Systems, of which the following is a full, clear,'concise, and exact description.

This invention relates to transmission systems and more particularly to four-wire telephone repeater systems.

An object of this invention is to provide improved signaling means for systems of this character.

Another object of the invention is to provide improved means for controlling the transmission efliciency of systems of this character.

In four-wire telephone repeater systems as usually constructed, two separated stations are connected by two separate transmission lines suitably connected, preferably inductively, at each end with a twowire terminating circuit. Therefore, with respect to either terminal station of the four-wire telephone repeater system, one transmission line is an outgoing circuit and the other an incoming circuit, both of which are inductively associated with the terminating circuit thereat.

In accordance with a feature of this invention, a four-wire telephone repeater system having outgoing and incoming circuits inductively associated with the terminating circuits, is provided with an outgoing ringing response relayin the terminating circuit for controlling the connection of a source of ringing current with the outgoing circuit and the disconnection of the incoming from'the'ter'minating circuit while ringing current'is connected withthe outgoing circuit, and with an incoming ringing response relay in the incoming circuit for controlling the connection of a source of ringing current with the terminating circuit and the disconnection of the incoming from the terminating cirouitflwhile ringing current is connected thereto. The incoming, outgoing and terminating circuits are so connected that both ringing response relays may respond upon the application'of ring.- ing current to either the terminating or the incoming, circuit, but apparatus provided in the incoming and terminating circuits pre vents the continued response of the incoming ringing response relay when ringing current is applied to the terminating circuit and prevents the continued response of the outgoing ringing response relay when ringing current is applied to the incoming circuit.

Inasmuch as the impe ance of an operators set may be materia ly different from that of two-wire lines, which may be connected with and form extensions of the terminating circuits of a four-wire repeater system, it has been customary to provide artificial linesor networks connected in the system of circuits, to obtain the proper transmission efliciency between operators sets connected with the separated terminating circuit. Since a terminating circuit may be connected with two-wire telephone lines having different characteristics, it has also been customary to provide apparatus for maintaining the transmission efliciency of the system substantially constant irrespective of the character of the lines with which the terminating circuit is connected. This has been accomplished by means of artificial lines or networks of the proper impedance, which are automatically connected in circuit when the terminating circuit is connected with certain types of four-wire lines. In accordance with the present invention the connection of these artificial lines or networks with .the system is brought about by electromagnetic switching devices controlled over one of the talking circuits of the fourwire telephonerepeater system, thereby reducing the amount of control apparatus required, and simplifying the entire system. For a more complete understanding of this invention, reference should be had to a terminal stations A and B, and with which is connected an intermediate repeater station 7 C, the apparatus shown in Fig. 2 being provided at terminal station A, that in Fig. 3 at repeater station 0, and that in Fig 4 at terminal station B. The repeater circuit comprises a transmission line B for the transmission of talklng currents and ringing signals in one direction, transmission line N for the transmission of talking current and ringing signals in the opppsite'diwith the terminating circuit M of the fourwire repeater circuit, and a link circuit H, provided at terminal statlon B, as shown in Fig. 5, may be employed in connecting the terminating circuit N of the four-wire repeater circuit with either a toll line K or i a toll switching trunk circuit L. The terminating circuits -M and N are each provided with artificial lines so that the so-called singing of the repeating elements is prevented and at the same time provides an eflicient talking circuit between the operators. when there are no telephone lines connected with the respective termlnating circuits. There is also provided means whereby when a telephone line is connected with the respectiveterminating circuit and the operators telephone sets are disconnected that these artificial lines will be disconnected, depending of course upon the terminating circuit withwhich the telephone line is connected. The impedance characteristics of the toll line K are different from those of the toll switching trunk circuit L.

A repeating coil having primary windings 5 and secondary windings 6, and autotransformers 9 and 10 are provided at station A for inductively associating-the terminating circuit M with the outgoing end of transmission line E and with the incomlng end of transmission line W. A similar repeating coil having primary windings 11 and secondary windings 12, and similar auto-transformers 13 and 1 1 are provided at terminal station B for inductively asso: ciating the terminating circuit N with the incoming end of the transmission'line and the outgoing end of the transmission line W. There is also provided at station A an artificial balancing line 15 for Ibalanc ing the telephone line, which maybe connected with terminating circuit M, and a similar artificial balancing line 16 is provided at station B for balancing the line' connected with the terminating circuit N.

In order to balance the four-wire repeater system when an operators telephone set and no telephone line is connected with the respective terminating circuits thereof to prevent the so-called singing of therepeating elements and to provide efiicient talking circuits between operators, artificial lines 17 and 21 are provided at the respective terminal stations A and B- The artificial line 17 comprises series resistances 18, 18 and a bridged resistance 19 and condenser 20, while the artificial line 21 comprises similar series resistances 22, 22 and bridged resistance 23 and condenser 24. These artificial lines 17 and 21 are connected in the respective terminating circuit portions of the fourwire repeater system. These artificial lines are so proportioned that the impedance thereof simulates the impedance of the telephone lines which may be connected with the respective terminating circuits, so that these artificial lines may be balanced by the respective permanently connected artificial lines 15 and 16. When, however, a .tele-, phone line is connected with either terminatingcircuit and the operators telephone set is disconnected, artificial line 17 or 21,

vsion efliciency over the four-wire telephone repeater system. when the terminating circuit N thereof is connected to either a toll line or a toll switching trunk circuit, there is provided at the terminal station B two artificial lines 25 and- 26 respectively connected in the transmission lines W and E and each of which comprises series resistances 27 and a bridged resistance 28 and condenser 29. When the terminating circuit N of the fourwire telephone repeater system is connected with a toll switching trunk L, the artificial lines 25 and 26 are cut into the circuit, while when connection is made with the toll line K these artificial. lines are out of the circuit.

' With this general description in mind, the invention may now be fully understood from a description of the operation of the erating and slow-releaslng relay 34 operates over a circuit from batterv through the middle contact of relay 61, windin of relay 34.

and contact of relay 35 to ground. A cir: cuit is simultaneously closed throughlamps 36 and slow-operating relay 37. Relay "34,

however, operates before relay 37 is fully energized, and opens the circuit thereof,

thereby preventing the operation of this relay 37 and the lighting of the lamp 36; The insertion of plug 32 into jack 33 causes the operation of relays 38 and 39. The opera tion of relay 39 causes the energization of relay 40 (Fig. 3) over a circuit from battery through the winding of relay 40, left-hand windings of repeating coil 41 in parallel, over the two sides of transmission line E in parallel, the right-hand windings of repeating coil 42 in parallel, normal contact of outgoing ringing response relay 43, and the right-hand alternate contact of relay 39 to ground.

The operator at station A may now signal the operator at station B byactuating ringing key 45 to connect, a source of ringiii/g current 46 with the terminating circuit Ringing response relay 43 is traversed and energized by current from the source 46 and upon being energized opens its normal and closes its alternate contact. The opening of the normal contact opens the circuit of and denergizes relay 40. The closure of the alternate contact causes the operation of a quick-operating and slow-releasing relay 47 which in operating opens its normal contacts, thereby disconnecting from the terminating circuit M the incoming end of the transmission line W. The closure of the upper alternate contact of relay 4? causes the energization of a slow-operating and slowreleasing relay 48 over a circuit from battery through the winding of relay 48, alternate contact of relay 47, alternate contact of outgoing ringing response relay 43, and the right-hand alternate contact of relay 39 to ground. I

Ringing current from the source 46 which causes the energization of outgoing ringing response relay 43 also traversesthe windings of auto-transformor 9 series resistances 18 of the impedance arrangement 17, primary windings 5, the windings of the autotransformer 10', and the winding ofan incoming ringing response relay 49. Due to the impedance of the windings ofthe repeating coil and the auto-transformers, the amountof current traversing the windings of the incoming ringing response relay will be very much reduced, but still may, under some circumstances, be sufficient to cause the energization of this relay 49. Upon such anenergization of the incoming ringingre- 'sponse relay 49, a quick-operating and slowreleasing relay 50 is energized. The energization of this relay 50 causes the energizar tion of a slow-opearting and quick-releasing relay 51 The full energization of relay 51 closes thecircuit of a slow-operating relay 52. However, should the incoming ringing response relay- 49 respond to ringing current from the source 46, the slow-operating relay 52 cannot be fully energized'for the reason that before the chain of relays 50, 51,52 can become completely energized, the quick-operating relay 47 operates and opens the -.circuit of the incoming ringing response' relay 49, whereupon relays 50, 51, 52

will be released. By providing an arrangevator at the terminal station -B.

ment of this kind, it is possible to connect both the outgoing and the incoming ringing response relays; for it will be evident that should relay 52 become fully energized, the circuit of outgoing ringing response relay 43would then be opened and ringing current from source 53 will be connected with the cord circuit D.

The operation of the slow-operating and slow-releasing relay 48 connects a source of ringing current 54 in circuit with the lefthand winding of the repeating coil 42, whereupon current is induced into the righthand windings thereof and traverses the two sides of the outgoing end of the transmission line E. The current traversing this circuit also traverses the left-hand windings of repeating coil 41, whereupon a similar current is induced in the right-hand windings thereof, which are in circuit with the left-hand windings of repeating coil 55 associated with the incoming end ofthe transmission line E at terminal stationiB. Current will thereupon be induced into the right-hand windings of the repeating coil 55 and cause the 'energization of incoming ringing response relay 56. Upon the energization of this relay 56, a quick-operating and slow-releasingrelay 57 operates to complete a locking circuit for itself from battery through its ownwinding and the left-hand normal contact of relay 58 to ground. The clbsure of. the righthand, contact of relay57 causes the energization of a slow-operating and quick-releasing relay 59- and the lighting of the lamp 60. The "lighting of this lamp 60 serves as a line signal to the operl pon the restoration of the ringingkey 45 to normal position, outgoing ringing response relay 43, relays 47 and 48, and incoming ringing response relay 56, are deenergi'zed. The deenergization of relay 43 causes'the re'nergiz'ation of relay 40 (Fig. 3).

The operator at station B, observing the lighted. condition of the lamp 60, may insert plug 65 of the cord cir'cuit H into ack 66 of the terminating circuit N, whereupon relays 67 and 58 are energized. The energization of relay 58 opens the locking circuit of relay 57, whereupon this relay releases, causing the release of relay 59 and the extinguishment of the lamp 60. The closure of the left-hand alternate contact of relay 58 causes 71, and the left-hand alternate contact of relay 58 to ground. Both relays 40 and 68 being energized, a circuit is completed, causing the operation of relays 72, 73, 74,75 and 76. The operation of relay 74 connects a source of current with the transmitting elements of repeaters RE and RW associated with the respective transmission lines E and W. The operation of relays 72 and 73 connects the repeater RE into the transmission line E, and the operation of relays 75 and 7 6 connects the re eater RW into the transmission line W. he energization of relay 67 causes the operation of a quick-operating and slow-releasing rela 77 over a circuit from battery through til relay 67, winding of relay 77, and the contact of relay 78 to ground. Simultaneously with the closure of the circuit through relay 77 a circuit is closed through a lamp 79 and 'the winding of the slow-operating relay 80 However, relay 77 operates be- I in parallel. fore relay 80 is fully energized, and in oper* ating opens a circuit of relay 80, thereby preventing the operation of this relay and the lighting of the lamp 79. i

While the plugs of the cord circuit Dare connected with the 'acks of line F and the terminating circuit lll, keys 45 and 81 splitting key 44 and listening key 82 in normal position, relay 83 is energized over a circuit from battery through the winding of relay .83, the middle windings of the auto-transformer 9 in parallel, lower and middle contacts of relay 47 in parallel, normal contacts of relay 52 in parallel, tip and ring contacts of the jack 33 and the plug 32 in parallel, upper and middle normal contacts of ringing ke 45 in parallel, windings of retardation ,coil 84 in parallel, left-hand contact of relay 38, lower contact of relay 61, lower normal contact of ringing key 81, lower normal contact of listening key 82, lower normal contacts of splitting key'44, and lower normal contact of ringing key 45 to ground. The energization of,relay 83 disconnects the bridge element of the artificial line 17 and short-circuits the series elements thereof, thereby removing this artificial line from thefour-wire telephone repeater s stem. Upon the actuation of thelistening ey 82 or the splitting key 44 and the listening key 82 by the operator at the terminal station A,the operators telephone set is connected in circuit, and relay 83 is denergized to connect the arti ficial line 17 in circuit.

The operator at the) terminal station B, either before or after connecting the cord circuit H with the terminating circuit N, may actuate listening-key 85 to connect the operators telephone set in circuit. The operator at terminal station A may now instruct the operator at station B as to the connection desired, whereupon the listening e lower contact of and with th'e' ringing,

keys are restored to normal position and the operator at terminal station B inserts plug 86 into lack 87 of the toll switching trunk circuit The restoration of the listening key 82 or the listening key and the splitting key 44 to normal position by the operator at station A causes the energization of relay 83 to remove the artificialline 17 from circuit. The insertion of the plug 86 into the jack 87 causes the operation of relay 88 over .a circuit from battery through the winding of relay 88, winding of marginal relay 89, sleeve contacts of the plug 86 and the jack 87, and high resistance 90 to ground. Marginal relay 89 does not operate when included in circuit with high resist per and middle normal contacts of ringing key 96 in parallel, windings of retardation coil 97 in parallel, lower contact-of relay 98, upper contact of. relay 67, lower contact of relay 91, lower normal contact of ringing key 99, lower normal contact of listening key 85, lowr normal contacts of splitting key 100, and the lower normal contact of ringing key 96to ground. The operation of relay 92 causes the energization of relay 101, which upon attracting its armatures disconnects the bridge elements of the artificial line 21 and short-circuits the series elements thereof, thereby removing this artificial line 21 from circuit. The energization of marginal relay 93 causes the operation of relays 102 and 103, which in operating remove the short circuits of the series elements of the artificial lines 25 and 26 and establish the bridged elements of this artificial line, thereby connecting these two impedance elements 25 and 26 in circuit.

If the'operator at station B had connected the cord circuit H with the toll line K, the insertion of the plug 86 into jack 104 thereof would cause the operation of relay 88 and also marginal relay 89. The reason for this is that'resistance 105 connected with the sleeve terminal of the jack 104 is' of low resistance, which permits the operation of marginal relay 89. The operation of mar ginal relay 89 disconnects supervisory signal control relay 106 from acrossthe talking strands of the cord circuit H. 'Ma'rginal relay 89 in operating also causes the operation of relay 98, which short circuits condensers 107 and 108 connected in the respective talking strands of the cord circuit H, and removes a short circuit about resistance 109. Resistance 109 is thereupon included in the energizing circuit of relay 92 and marginal relay The adjustment of relay 93 is such that when this resistance 109 is included in its energizing circuit, the-marginal relay 93 will not be sufficiently energized to attract its armature, whereupon relays 102 and 103 will not be 0 )erated. Consequently, when cord circuit is connected with the toll line, the artificial lines 25 and 26 are not connected in circuit.

If the operator at station A, after the connection has been established between the two-wire telephone line F and either the toll line K or the toll switching trunk circuit L by way of the four-wire repeater system, desires to signal theoperator at station B, this may be done by actuating ringing key 45. The actuation of this key 45 first opens its normal contacts, thereby causing the denergization of relay 83 which again connects the artificial line 17 in circuit. The connection of the source of rin ing current 46 to the terminating circuit by the actuation of ringing key 45 causes the energization of the outgoing ringing response relay 43 as before, whereupon relay 40 is released. The release of this relay 40 causes the denergization of relays 72, 73, 74, 75

and 7 6, thereby disconnecting the repeaters RE and RlV from the transmission lines E and W. Upon the energization of ringing response relay 43, relays 47 and 48 operate as before. Ringing response relay 49 may also respond, but as before described, before it can cause the connection of ringing current from source 53 to the cord circuit, its own circuit is interrupted at the contacts of relay 47. As a result of the operation of relay 48, the source of ringing current 54 is connected with transmission line E and incoming ringing response relay 56 is energized. Relays 57 and 59 are thereupon energiz ed. Relay 95 is thereupon operatedovef a circuit from batterythrough thewinding of relay 95, middle alternate contact of relay 5'8, lower contact of relay 59 and the right-hand contact of relay 57 to ground. Relay 95 in operating connects a source of ringing current 115 with the cord circuit H,

thereby causlng the operation of relay 78 over a circuit from the source of ringlng I current 115, lower alternate contact of relay 95,- ring contacts of the engaged jack 66 and plug 65, middle normal contact of ringing key 96, upper winding of relay 78, condenser 116, lower windlng of relay 78, up-l per normal contact of ringingkey 96, tip

contacts of the engaged plug 65 and jack 66,

and the upper alternate contact of relay 95 to ground. If the cord circuit is connected withthe toll lineK, the'energizing circuit of relay 78 then includes the upper and middle contacts of relay 98, whereas if the cord circuit is connected with the toll switching trunk circuit L, the energizing circuit of relay 7 8 includes the condensers 107 and 108. The energization of rela 78 opens its contact, thereby causing the re ease of relay 77. Upon the release thereof, relay 80 is energized over a circuit from battery through the lower contact of relay 67, winding of relay 80, contact of relay 77, and the upper normal contact of listening-key 85 to ground. Upon the operation of relay 80 a locking circuit is established therefor through its own contact, whereupon the lamp 79 is maintained lighted over a circuit from battery through the lamp 79, contact of relay 80, and the upper normal contact of listening-key 85 to ground. The ringing key 45 may then be restored to normal position, thereby causing the reenergization of relay 83, the denergization of relays 43, 47 and 48 the energization-of relays 40, 72, 73, 74, 5 and 76, and the denergization of relays 56, 57, 59, 95 and 78. The operator at station B observing the lighted condition of lamp 79 may manipulate splitting ke 100 to actuate the left-hand contacts thereo opening up the cord circuit H and may then actuate listening key 85 to connect the operators set with the left-hand end of the cord circuit H. The actuation of the splitting key 100 and the listening key 85 causes the release of relays 92 and 101, whereupon the artificial line 21 is connected in circuit. If the cord circuit H is connected with the toll switching trunk circuit L, then the actuation of the listening key 85 also causes the release of marginal relay 93 and relays 1 02 and 103 to disconnect the artificial lines 25 and 26. Likewise, when the operator at station A actuates listening key 82, the relay 83 is denergized to connect the artificial line 17 in circuit. The connection of these artificial lines in the circuit provides for the proper transmission between the operators at the teriiiiiiak'stations, 'andba'lances the respective artificial lines 15 and 16 to prevent'the singing of the repeaters.

Should it be necessary for the operator at station B to signal the operator at station A, this may be accomplished by actuating ringing key 96. The actuation of ringing key 96 then connects a source. of ringing current 120 with the terminating circuit N, thereby causing the operationof the outgoing ringing response relay 71. The opening of the lower normal contact of ringing key 96 causes'the release of relays 92 and 101, and if marginal relay 93 is operated,'then also the release of relays 93, 102 and 103. The opening of the normal contact of relay 71 causes thedenergization of relay68, whereupon relays 72, 73, 74, 75 and 7 6 are released to remove the repeaters RE and RW from the transmission lines E and W. The closure of the alternate contact of outgoing ringing response relay 71 causes the operation of the quick-operating and slow-releasing relay 94 to open its normal and close its alternate contacts. The closure of the alternate contact of relay 94 causes the operation of a slow-operating and slowreleasing relay 121, which connects a source of ringing current 122 with the outgoing end of the transmission line W to cause the operation of the incoming ringing response relay 49 associated with the incoming end of the transmission line 'W. Relay 49 in operating causes the energization of the quick-operating and slow-releasing relay 50, whereupon the slow-operating and quick-releasing relay 51 operates. Relay 52 then operates over a circuit from battery through the winding of relay 52, left-hand alternate contact of relay 39, lower alternate'contact of relay 51, and the left-hand contact of relay 50, to ground. The operation of relay 52 connects the source of ringing current 53 with the cord circuit D, energizing the relay 35. The energizing circuit of which may be traced from the source of ringing current 53, lower alternate contact of relay 52, ring contacts of the jack 33 and the plug 32, middle normal contact of the key 45, lower normal contact of splitting key 44, winding of relay 35, upper and middle normal contacts of splitting key 44, upper normal contact of ringing key 45, tip contacts of the plug 32 and the jack 33, and the upper alternate contact of relay 52 to ground. The opening of the normal contact of relay 35' permits the release of relay 34, which in closing its contact causes the energization of the slow-operating relay 37. Relay 37 upon being ener ized establishes a locking circuit for itsel through its contact and the normal contact of listening-key 82 and maintains the lamp 36 lighted. The lighting of this lamp 36 serves as a signal to the operator at the station A. The restoration of the ringing key 96 to normal position by tl'ie'o'perator at station B causes the release of outgoing ringing response rela r 71, relays 94 and 121, the energization o the relays 92, 101, 68, 72, 73,74, 75 and 76, the release of incoming ringing response relay 49 and relays 50, 51, 52 and 35 and the energization of relay 34. The operator at station A, upon observing the lighted condition of the lamp 36 may actuate the listening key 82, which opens the locking circuit of relay 37, thereby extinguishing the lamp 36.

Since the outgoing ringing response relay 43 is connected in parallel with the winding of the incoming ringing response relay 49,ringing current incoming over the transmission line WV will also traverse the winding of outgoing ringing response relay 43, but due to the impedance of the windings of the repeating coil and the auto-transformers 9 and 10, the amount of the current traversing the windinglof relay 43 will be very much reduced. owever, there may be suflicient current to cause the operation of relay 47, and the consequent closure of the circuit of the slow-operating rela 48. Before this relay 48 can become sufii ciently energized to close its alternate contacts, slow-operating and quickreleasing relay 51 is operated to open the circuit of the outgoing ringing response relay 43. .It will therefore be apparent that with the organization of circuits and apparatus as shown and described, no interference results from the connection of. the outgoing ringing response relay 43; and the incoming ringing response relay 49 in circuit, so that both are traversed by rlnging current whether outgoing or in-,

coming. The organization ofthe circuits and apparatus associated with the incoming end of the transmission line E, the outgoing end of the transmission line W and the terminating circuit N are such that the same relation exists between the incoming ringing response relay 56 and the outgoing ringing response relay 71, as described in connection with relays 43 and 49, and there is, therefore, no interference between these two relays.

If a call should originate at the terminal station B the connection of the plug 65 with the jack 66 and the actuation of the ringing key 96, causes the energization of the outgoing ringing response relay 71, relays 94 and 121, incoming ringing response relay 49 and relays 50 and 51. Upon the energization of relay 50 a locking circuit is established therefor, which may be traced from battery through the winding and right-hand contact of relay 50, and the right-hand normal contact of relay 39. Relay 51 in operating causes the lighting oflamp 125 over a circuit from battery through the upper alternate contact of relay 51, middle normal contact of relay 39, and the lamp 125 to ground. The lighting of this lamp 125 serves as'a line signal to the operator at station A. From the previous descriptions the other operations in completing connections with the line F will be apparent without a detail description thereof.

While several sources of ringing or alternating current have been describedas being located at each terminal station, it istobe understood that there may be and usually is but one such sourceat each station with the necessary leads to the appropriate relays. This is also true with respect to theseveral batteries at the different stations.

From the foregoing description, it will be apparent that in employin the features of this invention there is pro uced a four-wire telephone repeater circuit over which it is possible to signal in both directions without any interference, By operating the relays for controlling the balancing networks over a simplex circuit made up of the two sides of a talking circuit which includes portions of a trunk or cord circuit and a four-wire repeater circuit, the number of conductors and relays required is very materially reduced, resulting in a very much simplified organizationof circuits and apparatus.

What is claimed is:

1. In a telephone transmission system, in combination, an incoming and an outgoing circuit, a terminating circuit inductively associated with the incoming and outgoing circuits, a ringing response relay in the terminating circuit, a source of ringing current, and means controlled by the ringing response relay for connecting the source of ringing current with the outgoing circuit and disconnecting the incoming circuit from the terminating circuit. I

2. In a telephone transmission system, in combination, an incoming and an outgoing circuit, a terminating circuit inductively associated with the incoming and outgoing circuits, a ringing response relay in the terminating circuit, a source of ringing current, a relay controlled by the ringing response relay for connecting the source of ringing current to the outgoing circuit, and another relay controlled by the ringing response relay for disconnecting the incoming circuit from the terminating circuit.

3. In a telephone transmission system, in combination, an incoming and an outgoing circuit, a terminating circuit inductively associated with the incoming and outgoing circuits, a ringing response relay in the terminating circuit, a source of ringing current, a relay controlled by the ringing response relay for disconnecting the incoming from the terminating circuit, and a third relay controlled by both the ringing response and disconnect relays for connecting the source of ringing current with the outgoing circuit.

4. In a telephone transmission system, in combination, an incoming and an out oing circuit, a terminating circuit inductive y associated with. the incoming and outgoing circuits, a ringing response relay in the incoming circuit, a source of ringing current, and means controlled by the ringing response relay for connecting the source of ringing current with the terminating circuit anddisconnecting the incoming from the terminating circuits.

5. In a telephone transmission system, in

combination, an incoming and an outgoing circuit, a terminating circuit inductively as: sociated with the incoming and outgoing circuits, a ringing response relay in the incoming circuit, a source of ringlng current, a relay controlled by the ringing response relay for connecting the source of ringing current with the terminating circuit, and a third relay controlled by the ringing response relay for disconnecting the incoming from the terminating circuit.

6. In a telephone transmission system, in combination, an incoming and an outgoing circuit, a terminating circuit inductively associated with the incoming and outgoing circuits, a source of ringing current, a ringing response relay in the incoming circuit, a relay controlled by the ringing response relay for disconnecting the incoming from the terminating circuit, and a third relay controlled by both the ringing response and the disconnecting relays for connecting the source of ringing current with the terminating circuit.

' 7. In a telephone transmission system, in combination, incoming and outgoing and terminating circuits, inductive devices for repeating the signals from the terminating to the outgoing circuit and from the incoming to the terminating circuit, an outgoing ringing response relay connected with the terminating circuit, a source of ringing current, a relay energized upon the response of the ringing response relay to disconnect the inductive devices from the terminating circuit, a third relay energized upon the response of the outgoing ringing response relay to conrect the source of ringing current with the outgoing circuit, a ringing response relay connected with the incoming: circuit, a relay energized upon the response of the incomingn'inging response relay for disconnecting the incoming circuit from the inductive devices, and another relay energized upon the response of the incoming ringing response relay for connecting the source of ringing current with the terminating circuit.

8. In a telephone transmission system, in combination, an incoming and an outgoing circuit, a terminating'circuit inductively associated with the incoming and outgoing circuits, an outgoing ringing response relay connected with the terminating circuit, an

incoming ringing response relay connected with the incoming circuit, means for applying ringing current to either the terminating or' incoming circuits whereby both ringing "response relays are energized, a source of rlnglng current, means controlled by the outgolng ringing response relay for connecting the source of ringing current with the outgoing circuit, means controlled by the incoming ringing response relay for connecting the source of ringing current with the terminating circuit, a relay energized upon the response of the outgoing ringing response relay when energized by ringing current applied to the terminating circuit to disconnect the incoming from the terminating circuit, thereby preventing the terminating ringing current connecting means from becomlng effective, and a relay energized upon the response of the ringing re-, sponse relay when energized by current ap plied to the incoming circuit fordisconnecting the incoming from theterminating circuit, thereby preventing the outgoing ringing current connecting means from becoming effective.

9. In a telephone transmission system, in combination, a transmission line comprising a pair of talking conductors, telephone lines ofdifi'erent types, a link circuit for connecting' the transmission line with the telephone lines, and means in the transmission line controlled over the talking conductors for automatically varying the transmission efiiciency of said transmission line in accordance with the type of telephone line with which the transmission line is connected.

10. In' a telephone transmission system, in combination, a transmission line comprising a pair of talking conductors, telephone lines of different types, a link circuit for connecting the transmission line with the telephone,

lines, and a relay in the transmission line controlled over the talking conductors for automatically adjusting'the transmission efficiency of the transmission line'in accordance with the requirements of the telephone line with which it is associated.

11. In a telephone transmission system, in combination, a transmission line comprising a pair of conductors, a tollline, a trunk circuit, a link circuit for connecting the transmission line with either the toll line or the trunk circuit, an artificial line, and a relay in the transmission line controlled over the talking conductors and operating when the transmission line is connected with the trunk circuit for including the artificial line in the transmission line.

12. In a telephone transmission system, in combination, a transmission line comprising a pair of conductors, a toll line, a trunk circuit, a link circuit for connecting the transmission line with either the toll llne or trunk circuit, an artificial line, and a marginal relay operating over a circuit including the talk ing conductors when the transmission line is connected with the trunk circuit to include the artificial line in the transmission line and a relay operating when the transmission line is connected with the toll line to prevent the operation of the marginal relay.

13. In a telephone transmission system, in combination, a transmission line comprising a pair of talking conductors, a toll line, a trunk circuit, a link circuit for connecting the transmission line with either the toll line or trunk circuit, anflartificial line, a

-marginal relay energized over a circuit including the talkingconductors and a por tion ofthe link circuit when connected-with the transmission line and the trunk circuit to include the artificial line in the transmission line, a resistance ,coil, and -a relay in the link circuit operating upon connection thereof with the toll line to include the resistance coil in circuit with themarginal relay thereby preventing its operation.

14. In a telephone transmissionsystem, in combination, a transmission line comprising talking conductors, an artificial line comprising series and bridgeresistances normally connected in the transmission line, a telephone line, a link circuit, and means operating over a circuit including the talking conductors upon the connection of the link circuit with the transmission and telephone lines for disconnecting a portion of the artificial line from the transmission line.

15. In a telephone transmision system, in combination, a transmission line comprising talking'conductors, an artificial line comprising series and bridge resistances normally connected in the transmission line, a telephone line, a link circuit, and a relay energized over a circuit including the talking sistances, said bridged resistances being normally disconnected from the transmission line, a trunk circuit, means controlling the connection of the bridged resistance of the second artificial line with the transmission line, and an operatin circuit including the talking conductors o the transmission line completed upon connection ofthe link circuit with the transmission and toll lines,

causing the operation of the first means, and means for altering the operating circuit when the linkcircuit is connected with the transmission line and the trunk circuit for causing the operation of both artificial line contro ling means.

17. In atelephone transmission system, in combination, a transmission line comprising talking conductors, an artificial line nor-v mally connected with the transmission ,line, arelay controlling the disconnection of a portion of the artificial line fromithe transmission line, a second artificial line comprising series and bridged resistances; said bridged resistances being normally disconnected from'the transmission line, a marginal relay controlling the connection of the second artificial line with the transmission line, a toll line, a trunk circuit, a link circuit, an operating circuit for both relays established ufion the connection of a link circuit with the toll line and the trunk circuit and including the talking conductors of the transmission line, and means responsive to the connection of the link circuit with the toll line for increasing the resistance of the operating circuit, thereby to prevent the operation of the marginal relay In witness whereof, I hereunto subscribe my name this 19th day of July, A. D. 1918.

PERCY M. GARDANIER. 

